netdev - Re: [PATCH v2 net-next] tcp: make connect() mem charging friendly

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Message-ID: <1416497628.8629.24.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 20 Nov 2014 07:33:48 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	ycheng@...gle.com, nuclearcat@...learcat.com,
	netdev@...r.kernel.org, ncardwell@...gle.com
Subject: Re: [PATCH v2 net-next] tcp: make connect() mem charging friendly

On Wed, 2014-11-19 at 14:57 -0500, David Miller wrote:
> From: Yuchung Cheng <ycheng@...gle.com>
> > 
> > Thanks! this simplifies the code a lot.
> 
> Agreed, applied, thanks everyone!

BTW, unless I am mistaken, it seems we can probably replace
memcpy_fromiovecend() by memcpy_fromiovec() and delete from
tcp_sendmsg() the annoying code skipping over the already consumed
bytes.

Something like this untested patch :

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c239f4740d10b10b67ef4fa44c831851fb9e1dcf..227540eef9d0870721258f9ddbace27b417c619e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1089,20 +1089,19 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb;
 	int iovlen, flags, err, copied = 0;
-	int mss_now = 0, size_goal, copied_syn = 0, offset = 0;
+	int mss_now = 0, size_goal, copied_syn = 0;
 	bool sg;
 	long timeo;
 
 	lock_sock(sk);
 
 	flags = msg->msg_flags;
-	if (flags & MSG_FASTOPEN) {
+	if (unlikely(flags & MSG_FASTOPEN)) {
 		err = tcp_sendmsg_fastopen(sk, msg, &copied_syn, size);
 		if (err == -EINPROGRESS && copied_syn > 0)
 			goto out;
 		else if (err)
 			goto out_err;
-		offset = copied_syn;
 	}
 
 	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
@@ -1151,15 +1150,6 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 		unsigned char __user *from = iov->iov_base;
 
 		iov++;
-		if (unlikely(offset > 0)) {  /* Skip bytes copied in SYN */
-			if (offset >= seglen) {
-				offset -= seglen;
-				continue;
-			}
-			seglen -= offset;
-			from += offset;
-			offset = 0;
-		}
 
 		while (seglen > 0) {
 			int copy = 0;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f5bd4bd3f7e669b3fd48a843d55e7313a30a3409..524e5b657e881a348f11def3f48f29a76f54fbab 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3049,8 +3049,8 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
 		goto fallback;
 	syn_data->ip_summed = CHECKSUM_PARTIAL;
 	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
-	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
-					 fo->data->msg_iov, 0, space))) {
+	if (unlikely(memcpy_fromiovec(skb_put(syn_data, space),
+				      fo->data->msg_iov, space))) {
 		kfree_skb(syn_data);
 		goto fallback;
 	}


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